GPIO state not retained after FOTA reboot on nRF54L15 (Zephyr SDK 3.0.2)

[Jishnu K J]

Hi,

I am using nRF54L15 with Zephyr RTOS in nRF Connect SDK v3.0.2.

After performing a FOTA update, the device reboots. I need to retain the state of a GPIO pin across this reboot.

The GPIO I am trying to retain is P1.06. I attempted to configure it with retention using the following code:

#define PIN_P1_06 38
#define P1_INDEX  6

void configure_retained_gpio(void) {
    // Configure the pin as output with retention enabled
    nrf_gpio_cfg_output(PIN_P1_06);
 
    NRF_P1->PIN_CNF[P1_INDEX] &= ~GPIO_PIN_CNF_CTRLSEL_Msk;
    NRF_P1->PIN_CNF[P1_INDEX] |= (GPIO_PIN_CNF_CTRLSEL_GPIO << GPIO_PIN_CNF_CTRLSEL_Pos);
}

However, after the OTA update and subsequent reboot, the GPIO state is cleared and does not retain the previous value.

My questions:

1. Is there any additional configuration required in nRF54L15 to retain GPIO states across a reboot after FOTA?

2. Is GPIO retention supported across MCU reset triggered by FOTA, or is it only supported for specific low-power modes?

Any guidance or recommended approach to preserve the GPIO state across OTA reboot would be greatly appreciated.

Thanks.

[Menon]

Hello,

I believe you only need to configure the mcuboot.overlay to initialize the pin in the bootloader. Regarding the issue you raised, does it occur only during DFU (FOTA)? Based on your description, the same behavior should also be observed during a normal reboot, such as after an assertion or a watchdog reset.

Kind Regards,

Abhijith

[Jishnu K J]

Hello Abhijith,

Yes, we observe the same behavior not only during DFU (FOTA), but also during a normal reboot.

In all these cases, the GPIO pin P1.06 (SYS_EN) returns to its default state after reset, causing the system to power off before the bootloader or application can reconfigure it.

Best regards,
Jishnu K J